Neurovirulence of herpes simplex virus type 1 depends on age in mice and thymidine kinase expression

Susceptibility to alphavirus infection is age dependent, and host maturation is associated with decreased virus replication and less severe encephalitis. To identify factors associated with maturation-dependent restriction of virus replication, we studied AP-7 rat olfactory bulb neuronal cells, which can differentiate in vitro. Differentiation was associated with a 150-to 1,000-fold decrease in replication of the alphaviruses Sindbis virus and Venezuelan equine encephalitis virus, as well as La Crosse bunyavirus. Differentiation delayed synthesis of SINV RNA and protein but did not alter the susceptibility of neurons to infection or virion maturation. Additionally, differentiation slowed virus-induced translation arrest and death of infected cells. Differentiation of uninfected AP-7 neurons was associated with changes in expression of antiviral genes. Expression of key transcription factors was increased, including interferon regulatory factor 3 and 7 (IRF-3 and IRF-7) and STAT-1, suggesting that neuronal maturation may enhance the capacity for antiviral signaling upon infection. IRF-7 produced by undifferentiated AP-7 neurons was exclusively the short dominant negative ␥-isoform, while that produced by differentiated neurons was the full-length ␣-isoform. A similar switch in IRF-7 isoforms also occurred in the brains of maturing C57BL/6J mice. Silencing of IRF expression did not improve virus multiplication in differentiated neurons. Therefore, neuronal differentiation is associated with upregulation of transcription factors that activate antiviral signaling, but this alone does not account for maturation-dependent restriction of virus replication. IMPORTANCEViral encephalomyelitis is an important cause of age-dependent morbidity and mortality. Because mature neurons are not readily regenerated, recovery from encephalitis suggests that mature neurons utilize unique antiviral mechanisms to block infection and/or clear virus. To identify maturational changes in neurons that may improve outcome, we compared immature and mature cultured neurons for susceptibility to three encephalitic arboviruses and found that replication of Old World and New World alphaviruses and a bunyavirus was reduced in mature compared to immature neurons. Neuronal maturation was associated with increased baseline expression of interferon regulatory factor 3 and 7 mRNAs and production of distinct isoforms of interferon regulatory factor 7 protein. Overall, our studies identified maturational changes in neurons that likely contribute to assembly of immunoregulatory factors prior to infection, a more rapid antiviral response, increased resistance to virus infection, and improved survival. Development of age-dependent resistance to fatal disease is a characteristic of many virus infections of the central nervous system (CNS) (1-9). We have used Sindbis virus (SINV), the prototype alphavirus in the family Togaviridae, as a model system to understand maturation-mediated restriction of virus multiplication in neurons. SINV preferentially i...

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“…Host maturity is an important factor determining the outcome of viral encephalitis (1,(3)(4)(5)(6)(7)(8)(9). We have previously demonstrated mat-…”

Section: Discussionmentioning

confidence: 99%

“…evelopment of age-dependent resistance to fatal disease is a characteristic of many virus infections of the central nervous system (CNS) (1)(2)(3)(4)(5)(6)(7)(8)(9). We have used Sindbis virus (SINV), the prototype alphavirus in the family Togaviridae, as a model system to understand maturation-mediated restriction of virus multiplication in neurons.…”

mentioning

confidence: 99%

Differentiation of Neurons Restricts Arbovirus Replication and Increases Expression of the Alpha Isoform of IRF-7

Schultz

Vernon

Griffin

2015

J Virol

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“…Age-dependent resistance to virus replication is also a characteristic of a number of other neurotropic viruses, including Semliki Forest virus (SFV) (14,15,43), Japanese encephalitis virus (JEV) (32,42,56), mouse hepatitis virus (48), measles virus (19,22), reovirus (39), blue-tongue virus (5), parvoviruses (6, 7), influenza virus (26), and herpesviruses (1,2,40,55). As with the AR339 strain of SV, infection of neonatal mice with the A7(74) strain of SFV leads to fatal encephalitis, but mice that are at least 2 weeks of age recover uneventfully (44).…”

Section: Discussionmentioning

confidence: 99%

Characterization of an In Vitro Model of Alphavirus Infection of Immature and Mature Neurons

Vernon

Griffin

2005

J Virol

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Terminally differentiated, mature neurons are essential cells that are not easily regenerated. Neurotropic viruses, such as Sindbis virus (SV), cause encephalomyelitis through their ability to replicate in neurons. SV causes the death of immature neurons, while mature neurons can often survive infection. The lack of a reproducible and convenient neuronal cell culture system has hindered a detailed study of the differences in levels of virus replication between immature and mature neurons and the molecular events involved in virus clearance from mature neurons. We have characterized SV replication in immortalized CSM14.1 rat neuronal cells that can be differentiated into neurons. During differentiation, CSM14.1 cells ceased dividing, developed neuronal morphology, and expressed neuron-specific cell markers. SV infection of undifferentiated CSM14.1 cells was efficient and resulted in high levels of virus replication and cell death. SV infection of differentiated CSM14.1 cells was less efficient and resulted in the production of 10-to 100-fold less virus and cell survival. In undifferentiated cells, SV induced a rapid shutdown of cellular protein synthesis and pE2 was efficiently processed to E2 (ratio of E2 to pE2, 2.14). In differentiated cells, the SV-induced shutdown of cellular protein synthesis was transient and pE2 was the primary form of E2 in cells (ratio of E2 to pE2, 0.0426). We conclude that age-dependent restriction of virus replication is an intrinsic property of maturing neurons and that the CSM14.1 cell line is a convenient model system for investigating the interactions of alphaviruses with neurons at various stages of differentiation.Viral encephalitis due to infection with arthropod-borne viruses is an important cause of mortality and often results in significant long-term neurological deficits in those that survive (8,31,46). The enveloped, message-sense RNA virus Sindbis virus (SV) is the prototype alphavirus in the family Togaviridae and is related to viruses known to cause encephalitis and arthritis in humans (47). Neurons are the primary target cell for SV in mice (28), and the outcome of infection is determined by both host and viral factors (20,21,37,50,52). An important host determinant is the maturity of the neuronal population infected. Immature animals replicate virus in the central nervous system (CNS) to higher titers than mature animals and are highly susceptible to fatal disease, dying within 3 to 4 days after infection (20,29,37). Adult animals infected with the same strain of SV survive and, in the absence of a virus-specific immune response, develop persistent infection (20, 34). Immunocompetent mature animals can recover from infection and clear virus from the CNS through noncytolytic mechanisms involving anti-viral glycoprotein antibody (34) and gamma interferon (3). However, an understanding of the mechanisms underlying these virus-host interactions has been hampered by the lack of a convenient in vitro system for study.The availability of a reproducible and convenient in vit...

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“…However, these genes are required for maximum demonstration of neurovirulence in various animal models and can thus be regarded as neurovirulence genes. These include virus-encoded enzymes involved in DNA metabolism such as thymidine kinase (Tenser et al, 1981;Ben-Hur et al, 1983;Brandt et al, 1991), ribonucleotide reductase (Cameron et al, 1988) and dUTPase (Thompson & Wagner, 1988;Pyles et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Characterization of the herpes simplex virus type 1 strain 17+ neurovirulence gene RL1 and its expression in a bacterial system

Ea¹,

Rg²,

Sm³

et al. 1994

Journal of General Virology

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The DNA sequence of herpes simplex virus type 1 (HSV-1) strain 17 + in the region coding for the polypeptide ICP34.5 predicts a protein of 248 amino acids with a proposed M r of 26158. The entire RL1 open reading frame was cloned into the expression vector pET8c to enable over-expression of ICP34.5 in Escherichia coli. The expressed protein was partially purified and used as an immunogen to produce a polyclonal antiserum in rabbits. Construction of an ICP34.5 null mutant (1771), demonstrated that the predicted open reading frame for ICP34.5 in strain 17 + is correct and confirmed that HSV-1 strain 17 + ICP34.5 specifically determines neurovirulence. The specificity of the antiserum directed against the E. coli-expressed ICP34.5 was defined by Western blotting of wild-type and RL1-negative infected cell extracts.

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Neurovirulence of herpes simplex virus type 1 depends on age in mice and thymidine kinase expression

Cited by 40 publications

References 22 publications

Differentiation of Neurons Restricts Arbovirus Replication and Increases Expression of the Alpha Isoform of IRF-7

Differentiation of Neurons Restricts Arbovirus Replication and Increases Expression of the Alpha Isoform of IRF-7

Characterization of an In Vitro Model of Alphavirus Infection of Immature and Mature Neurons

Characterization of the herpes simplex virus type 1 strain 17+ neurovirulence gene RL1 and its expression in a bacterial system

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